Ultrasonic nebulizer

ABSTRACT

There is provided a nebulizer for use with oxygen tent equipment for controlled inhalation therapy. The nebulizer includes a vertical cylinder defining a liquid chamber with a piezoelectric transducer that closes the bottom of the chamber. A predetermined level of liquid is maintained in the chamber in direct contact with the transducer. A high frequency power source is connected to the transducer to provide ultrasonic vibrations thereof. The fluid in the chamber will be nebulized and suitable conduit means are provided for connecting the chamber to the gas flow from the oxygen tent equipment.

United States item [72] lnventors Robert L. Weaver Toledo; Frank D.Myrice, Perrysburg, both of, @1110 [21] Appl No. 741,451 [22] Filed July1,1960 [45] Patented July 20, 1971 [73] Assignee Chemetron CorporationChicago, 111.

[54] ULTRASONIC NEBULIZER 3 Claims, 13 Drawing Figs.

[52] U.S.Cl 128/194,

128/i9l A [51] 1nt.Cl ..A6llm16/02 [50] Field of Search 128/2405,

194,193,195,196,l97,173,191, 191.1, DIG. 2; 103/26; 261/D1G. 48,1;239/338 [56] References Cited UNITED STATES PATENTS 2,852,022 9/1958Netteland 128/191 3,233,549 2/1966 Howe 103/26 3,387,607 6/1968 Gauthieret a1. 128/173 FORElGN PATENTS 1,056,065 4/1959 Germany 128/1941,103,522 3/1961 Germany 128/2405 Primary Examiner-Richard A. GaudetAssistant Examiner-.l. B. Mitchell At!0rney-Mason, Kolehmainen, Rathburnand Wyss ABSTRACT: There is provided a nebulizer for use with oxygentent equipment for controlled inhalation therapy. The nebulizer includesa vertical cylinder defining a liquid chamber with a piezoelectrictransducer that closes the bottom of the chamber. A predetermined levelof liquid is maintained in the chamber in direct contact with thetransducer. A high frequency power source is connected to the transducerto provide ultrasonic vibrations thereof. The fluid in the chamber willbe nebulized and suitable conduit means are provided for connecting thechamber to the gas flow from the oxygen tent equipment.

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flrrom/eys ULTRASONIC NEIBIUILIIZEIIR The present invention relates toan ultrasonic nebulizer, and to an oxygen tent apparatus for controllinginhalation therapy that utilizes an improved arrangement for nebulizingliquids. More specifically, the present invention relates to anultrasonic nebulizerwherein ultrasonic vibrations are provided toentrain minute particles of liquid into a gaseous stream,

In many therapeutic applications, it is desirable to provide a highhumidity atmosphere. This is frequently desirable in the circulation ofoxygen to an oxygen tent used for therapeutic purposes. The-temperature,rate of circulation, and concentration of the oxygen are controlled in asuitable control unit which may include refrigerating apparatus formaintaining a desired temperature of the oxygen containing medium. Inthe past, such an oxygen tent alone could not give I percent humidityatmosphere with uniform droplets in commercial installations. Moreover,a high humidity nebulizer, when used by itself, gives the patient 100percent humidity but the temperature inside the canopy has an insulatingeffect on the body which precludes cooling of the body by means ofperspiration and is likely to cause a hyperthermic condition of thepatient.

Heretofore it has frequently been desirable to provide a medicated gasflow containing medication vapor for therapeutic purposes. In such flowit is necessary to obtain finely divided particles of medicationdispersed within the gas flow.

Commercially available ultrasonic nebulizers generally provide atransducerdriven by a suitable oscillator circuit in an ultrasonicrange,.as; forexample, at 1.4 me. Since transducers of this type weregenerally subjected to corrosion from saline solutionsfrequentlydispensed thereby, it is common to cover the transducer with a layer ofdistilled water, which in turn is covered by a sealed, vibrationtransmitting diaphragm acting upon the solution to be dispersed. Suchsolution, which may be saline solution or other liquid, is then pouredinto the container on top of the diaphragm and subjected to supersonicvibrations. In the prior art device, the distilled water below thediaphragm was never nebulized and became very hot.

Moreover, difficulty has also been experienced with prior art nebulizersin transferring thenebulized vapors from the nebulizer to the gasstream.

Accordingly, it is an object of the present invention to provide a newand improved oxygen tent apparatus that results in a humidity atmosphereof I00 percent, with relatively uniform droplets.

A further object of the present invention is to provide a new andimproved nebulizer which overcomes the above mentioned difficulties.

Yet afurther object of the present invention is to new and improvedultrasonic nebulizer.

Yet another object of the present invention is to provide a new andimproved nebulizer for dispersing medication in finely divided particlesinto a gaseous flow.

Further objects and advantages of the present invention will becomeapparent as the following description proceeds and the features ofnovelty which characterize the invention will be pointed out withparticularity in the claims annexed to and forming a part of thisspecification.

In accordance with these and other objects, there is provided animproved oxygen tent apparatusfor therapeutic purposes that has animproved nebulizer. As is known in oxygen tent apparatus, such apparatusincludes a canopy for inhalation therapy, and a temperature and flowcontrol unit for regulating the flow of a gaseous medium to the canopy.Gas conduit means interconnect the temperature and flow control unitwith the canopy. In accordance with the present invention, an improvednebulizer is conveniently located at working height connected todisperse finely divided liquid particles into the provide a gas flowfrom the temperature and control unit to the canopy.

The improved nebulizer includes a vertical cylindrical housingwhichdefines a liquid chamber and which is closed at the bottom by apiezoelectric transducer. Means are provided for maintaining apredetermined level of liquid in the liquid chamber in direct contactwith the transducer. A high frequency power source capable of vibratingthe transducer at ultrasonic speeds is provided. A portion of the gasflow from the control unit to the tent is directed into the chamber ofthe nebulizer to help remove the nebulized vapors.

In accordance with another feature of the present invention, means areprovided for supplying a quantity of medication within the mechanicalinfluence of the ultrasonic vibrations. Conduit means are connected todisperse the finely divided ultrasonic medication into the stream of thegas.

Advantageously, the nebulizer according to the present inventionprovides up to I00 percent humidity with controlled temperature insideof the canopy. The droplets are uniform in size and small enough to befully utilized within the tent. Moreover, since the liquid above thetransducer is continuously replenishing the liquid being nebulized, thetransducer is maintained cool by the liquid. The movement of gas throughthe nebulizer chamber helps to remove the nebulized vapors.

For a better understanding of the present invention, reference may behad to the accompanying drawings wherein:

FIG. I is a fragmentary perspective view of a temperature and controlunit for an oxygen tent apparatus equipped with an ultrasonic nebulizeraccording to the present invention;

FIG. 2 is a fragmentary section, drawn to a larger scale, of the controlpanel of the unit of FIG. I; 7

FIG. 3 is a fragmentary elevational view of the gas flow system of thecontrol unit of FIG. 1, fragmentarily illustrated, and drawn to a largerscale with sections thereof being broken away; 7

FIG. 4 is a cross-sectional side elevational view of the gas flow systemof FIG. 3, taken along line 4-4 thereof;

FIG. 5 is a fragmentary cross-sectional view of the ultrasonicnebulizer, taken along line 5-5 of FIG. 3;

.FIG. 6 is a cross-sectional elevational view of the ultrasonicnebulizer taken along line 6-6 of FIG. 3, illustrating a safetyarrangement in more detail;

FIG. 7 is a cross-sectional plan view of the ultrasonic nebulizer takenalong line 7-7 of FIG. 6;

FIG. 8 is a schematic representation of a typical high frequencyoscillator source connected to drive the transducer of the ultrasonicnebulizer;

FIG. 9 is a fragmentary perspective view of the temperature and controlapparatus, having a modified form of ultrasonic nebulizer securedthereto for dispersing medication into the gas flow;

FIG. 10 is a fragmentary elevational view, partially broken away,illustrating the modified nebulizer of FIG. 9;

FIG. II is a cross-sectional view of the ultrasonic nebulizer of FIG. 9,taken along line 11-11 of FIG. I0;

FIG. 12 is a perspective view of a medication bag for use with theultrasonic nebulizer of FIG. 9; and

FIG. I3 is a fragmentary cross-sectional detail view of the medicationbag of FIG. I2, taken along line 13-13 thereof.

Referring now to the embodiment of FIGS. 1 through 8, there isillustrated an oxygen tent apparatus, generally illustrated at 20 inFIG. ll, including a temperature and flow control unit 21 connected to atherapeutic canopy, such as an oxygen tent by a suitable gas flow systemof duct work 25. The duct work includes a gas supply conduit 26 and agas return conduit 27. Each of the conduits 26 and 27 includes an elbow28 and 29, respectively, connected to the control unit 21 through aflexible coupling 30 and 31, respectively, and adapted to be connectedto the gas therapy canopy through a suitable connector conduit,illustrated fragmentarily in phantom in FlG.4as 32.

As is conventional with oxygen tent apparatus, the control unit 21normally houses air conditioning or refrigerating apparatus, under thecontrol of a temperature regulator 33, FIGS. l and 2, on a control panel34 ofthe control unit 21. In addition, the control unit will houseappropriate flow control equipment under the control of a flow regulator35. Thus, the oxygen tent apparatus 20 will supply therapeutic gas, suchas oxygen, under regulated temperature and flow conditions to a suitabletherapeutic canopy.

In accordance with the present invention, there is provided an improvedultrasonic nebulizer unit 38. The nebulizer unit 38 includes a nebulizerhousing 40, open at its top for receiving a supply bottle 41 of liquidto be nebulized into the gas stream in the gas supply conduit 26. Thesupply bottle 41 opens into a standpipe 42, FIG. 3, designed to maintainthe level of liquid 43 in the nebulizer chamber 41) at a desired height,as illustrated at 44, FIG. 3. The liquid 43 may be distilled water,saline solution, or other desired therapeutic solution.

To provide for the ultrasonic vibration of the liquid 43 within thenebulizer chamber 40, the bottom of the nebulizer chamber has a reduceddiameter cylindrical bore 45 closed by a concave transducer 50, whichmay be suitable piezoelectric crystal, such as a tourmaline composition.lt is resonant at the given frequency of the oscillator driving system,which in one embodiment was approximately 1.4 me. The transducer closesthe bottom of the bore 45, and an O-ring seal 51 forms a seal betweenthe transducer 50 and the nebulizer chamber 40.

To permit undampened vibrations of the transducer 50, the transducer 50is resiliently mounted by a wedge-shaped ring 52 bearing against itsunder surface through the bias ofa plurality of compression springs 53seated in recesses 55 in a closure cap 56. The closure cap 56 and alarge mass 39a of the nebulizer 39 forming the bore 45 together define aheat sink sufficient to dissipate undesirable heat.

To provide a solid state, fail-safe cutoff for the nebulizer unit 38, inthe event that the reservoir becomes empty and the liquid level in thetransducer chamber falls below a predetermined level, there is provideda suitable photoelectric control, generally illustrated at 58. Thephotoelectric control includes a light source 59 that is detected by asuitable photoconductive cell 60. A transparent level gage 61 isconnected to the nebulizer chamber 40 through a suitable fluid conduit62, FIGS. 6 and 7, so that the level of liquid within the level gage 61is the same as the liquid level 44 within the nebulizer chamber 40, asbest illustrated in FIG. 3. A float 63 of cork or other suitable opaquematerial floats on the fluid in the level gage 61. However, if the levelof fluid within the nebulizer chamber 40 drops to a predetermined level,thus dropping the level of fluid in the level gage 61, the float 63 willdrop with the lowering fluid until such time as it blocks the lightsource 59 from the photoconductive cell 60. At this time, the nebulizerunit 38 will automatically shut off. A suitable photoelectric controlcircuit 58 is described below.

To provide for electrical connection to the transducer 50, there isprovided a suitable electrical jack 66, one terminal 66a of which isconnected to the center of the transducer 50 by a suitable conductor 67,and the other terminal 66b of which is electrically connected to theperipheral edges of the transducer 50 through the ring 52 and ground.

To provide for a positive flow of gas through the nebulizer chamber 40to help remove the nebulized vapors, the nebulizing chamber 40 above thelevel of the fluid 44 is connected to the gas supply conduit 26 to passa portion of the gas flowing therethrough into and through the nebulizerchamber. More specifically, there is provided a nebulizer gas inletconduit 70 having an intake end 70a turned downwardly facing into theflow of gas to the supply conduit 26, and having its outlet end 70bextending into the nebulizer chamber 40 at a slight downward angle. Anebulizer gas outlet conduit 71 is vertically spaced above the gas inletconduit 70, having a discharge end 710 facing downstream of the gas flowin the conduit 26, as best illustrated in FIG. 4, and having a gas inletend 71!) extending from the nebulizer chamber 40. It will be understoodthat the dynamic effect of gas flow through the conduit 26 will effect aflushing of the nebulizer chamber 40 so as to remove the nebulizedvapors therefrom and to discharge the nebulized vapors into the gassupply conduit 26. Any suitable oscillator drive system may be used todrive the transducer 50 of the nebulizer unit. One suitable oscillatordrive system which may be incorporated into the control unit 21 isillustrated schematically in FIG. 8. An oscillator power supply systemis designed to provide radio frequency power for the ultrasonicnebulizer unit 38. The power supply 100 includes a conventional threewire plug 102 that may be plugged into any suitable source of 1 l7 voltalternating current. The power supply 100 is connected to the transducer50 by a shielded cable 104 terminated by a phone jack 105 ofa suitablesize to match the phone plug 66 extending from the transducer, andincludes a power line interlock switch 300 which prevents energizationof the nebulizer when the power supply is not connected to thetransducer.

The power supply 100 comprises generally a transformer 108, diode bridgerectifier circuit 110, a triode oscillatortube 112, a tank circuit 114,and associated circuitry. The transformer 108 includes a 117 voltprimary winding 116; a 6.3 volt, 6 ampere center tapped secondarywinding 124; and 800 volt, 200 milliampcre secondary winding 126; and a6.3 volt, l ampere secondary winding 127. One side 117 of the primarywinding 116 connects to the photoelectric control 58, the interlockswitch 300, the fuse 120, one side of the switch 122, the radiofrequency interference filter 123, and ultimately to the plug 102. Theother side 121 of the winding 116 connects to the fuse 118, to the otherside of the switch 122, the radio frequency interference filter 123, andultimately to the plug 102. The 6.3 volt secondary winding 124 isconnected to the filament terminals 128 and 130 of the triode oscillatortube 112, and supplies heating current to the filament of the tube 112.The 800 volt secondary winding 126 is connected in series with arheostat 132, having a control knob 132a on the control panel 34, andthe resulting series circuit is connected across input nodes 134 and 136of the rectifier circuit 110. The 6.3 volt secondary winding 127supplies power to the light source 59.

The rectifier circuit 110 includes eight rectifier diodes 138, 140, 142and 152. Each of these diodes has a current rating of one ampere and areverse voltage rating of at least 800 volts. The diodes are used inseries connected pairs so as to give each branch of the circuit 110 aneffective reverse voltage rating of at least 1,500 volts. The circuit110 includes the two input nodes 134 and 136, and also two output nodes154 and 156 that supply rectified current to the triode oscillator tube112. The node 154 is connected to each of the input nodes 134 and 136 bythe two series connected pairs of diodes 142 and 144, and and 152. Thesediodes are oriented so that their anodes face the node 154. The node 156is connected to each of the input nodes 134 and 136 by the two seriesconnected pairs of diodes 138 and 140, and 146 and 148. These diodes areoriented so that their cathodes face the node 156. The node 156 isconnected to a ground potential point 158 by a low ohmage resistor 160and by a fuse 162. The node 154 is connected to a ground 164 by theseries combination of a low ohmage resistor 166 and a pair of electroliccapacitors 168 and 170. Resistors 172 and 174, which are respectivelyconnected in parallel with capacitors 168 and 170, insure that the twocapacitors 168 and divide the rectifier circuit 110 output voltageequally between themselves. The rectifier circuit 110 output voltageappears as a negative potential at the node 176.

The triode oscillator tube 112 includes a filament that connects to thefilament leads 128 and 130, a grid that connects to node 176 by a seriescircuit that includes an inductor 184 and f the parallel combination ofa capacitor 186 and a resistor 188/ The inductor 184 provides a directcurrent path between the negative potential node 176 and the grid lead180. The inductor 184 is transformer coupled to an inductor 190 withinthe tank circuit 114, and therefore functions as a source of radiofrequency feedback voltage for the grid of the tube 112. The parallelcombination of the capacitor 186 with the resistor 188 self-biases thegrid terminal 180 to a potential somewhat more negative than thepotential of the tube 112 filament, thereby limiting the tube 112 platecurrent. A suitable tube for use in this circuit is an 812A.

The tank circuit 114 is a parallel combination ofan inductor 190 with afixed capacitor 192 and a variable capacitor 194. The tank circuit isconnected between the plate lead 182 of the triode oscillator tube 112and a ground potential point 196. The output signal from the tankcircuit 114 is taken between the ground potential point 196 and a tap198 upon the inductor 190. The ground potential point 196 is'connectedto the outer shield 199 of the cable 104, and the tap 198 is connectedto the outer shield 199 of the cable 104, and the tap 198 is connectedto the center conductor 201 of the cable 104. As noted above, theinductor 190 is transformer coupled to the inductor 184. r

Three capacitors are included in this circuit toprevent high frequencysignals from traveling between the triode oscillator tube 112 and thetransformer 108. A first capacitor 200 connects the node 176 to a groundpotential point 164 and prevents high frequency currents from flowingtowards the transformer 108 from the inductor 184. A second capacitor202 and a third capacitor 204 are connected respectively between thefilament leads 1 28 and 130 and ground potential points 206 and 208.These two capacitors 202 and 204 prevent high frequency currentsfromhflowing along the filament leads 128 and 130 towards thetransformer 108.

A fan 208 may be provided to cool the triode oscillator tube 112. i

A suitable photoelectric control system 58 is shown in FIG. 8. Thecontrol system 58 includes the light source 59 and the photoconductivecell 60, and also includes a capacitor 250, a four-layer switching diode252, a triac semiconductor switch 254, and a pushbutton switch 256. Thetriac switch 254 is connected in series with the input lead 117 to thetransformer 108 and therefore controls a flow of power to the nebulizer.The pushbutton switch'256 is connected in parallel with the triacswitch. The photoconductive cell 60 and the four-layer diode 252serially connect a control lead 255 on the triac switch 254 to one triacswitch lead 257. The photoconductive cell 60 and the capacitor 250serially connect the triac switch lead 257 to the triac switch lead 259,thus forming a potential dividing circuit.

The light source 59 normally illuminates the photoconductive cell 60 andmaintains the photoconductive cell 60 in a conducting state. Thecapacitance of the capacitor 250 is only 0.1 microfarad, so itsconductance may be ignored when the photoconductive cell 60 is fullyilluminated. Each time the alternating current supply voltage swingsthrough 0 volts, both the triac switch 254 and the four-layer diode 252turn off. When the supply voltage rises above the characteristic voltageof the four-layer diode 252, the diode 252 again conducts and turns onthe triac switch 254. For all practical purposes, the triac switch 254appears to conduct continuously when the photoconductive cell 60 isfully illuminated.

When the float 63 partially blocks the photoconductive cell 60 from thelight source 59, the conductivity of the photoconductive cell 60 drops.The conductance of the capacitor 250 can no longer be ignored, and thecapacitor and the photoconductive cell now function as a potentialdivider circuit. When the conductivity of the photoconductive cell 60drops to the point where the voltage developed across the capacitor 250no longer exceeds the characteristic voltage of the four-layer diode252, the diode 252 and the triac switch 254 will not turn on, and thenebulizer is deprived of power. The nebulizer thus turns off when thefloat 63 blocks the photoconductive cell 60 from the light source 59.

The light source 59 obtains energy from a secondary winding 127 on thetransformer 108. When the-nebulizer is turned off and the light source59 is extinguished, it is quite impossible for the nebulizer to turn on,even after the float 63 returns to its normal position. The pushbutton256 provides a means for momentarily bypassing the triac switch 254 andenergizing the nebulizer, and thus functions as a start control.

The operation of the radio frequency power supply 100 is conventional.The oscillator tube 112 functions as a tuned plate oscillator. Theparticular frequency generated can be controlled by varying thecapacitance of the variable capacitor 194, and in one embodiment wasadjusted to 1.4 megacycles. The amount of radio frequency energygenerated can be controlled by varying the setting of the rheostat 132.

In a particular embodiment of the invention it was found that a poweroutput in the range of approximately 45 to 50 watts workedsatisfactorily. The maximum plate dissipation of the tube 112 was 65watts. The power supply was used to drive a piezoelectric crystal, oftourmaline composition, one and seven-eighths inches in diameter. It wasresonant at the given frequency of the generator, which wasapproximately 1.4 mc. The heat sinkwas found sufficient to dissipate allundesirable heat. The transducer chamber was constructed of Lexan, andthe cap forming a part of the heat sink was formed of aluminum. Thereservoir bottle 41 had a capacity of 2,000 cubic centimeters, with asupply tube one-half inch in diameter. When the reservoir is invertedand placed into the transducer chamber, the liquid fills the chamber tothe level determined by the length of the supply tube. Water will flowonly when air is allowed to enter the reservoir through the supply tube.The fluid level in the transducer chamber 40 cuts off the air suppliedto the reservoir.

It may bedesirable to nebulize medication into the gas flow. Anembodiment of the ultrasonic nebulizer and connections thereof toaccomplish this result is illustrated in the embodiment of FIGS. 9through 13. Similar parts of this embodiment,

with the embodiments of FIGS. 1 through 8, are identified by the samereference numerals.

Referringnow to the embodiment of FIGS. 9 through 13, there isillustratedan ultrasonic nebulizer unit 75 adapted to nebulizemedication into the gas flow of an oxygen tent apparatus. As heretoforedescribed, the oxygen tent apparatus includes the temperature and flowcontrol unit 21 having the gas flow system 25 including the gas supplyconduit 26 and the gas return conduit 27. The gas supply conduit and thegas return conduit respectively include an elbow 28 and 29 connected tothe control unit 21 at a flexible coupling 30 and 31.

Referring now to the supersonic nebulizer unit 75 mounted on the gassupply conduit 26, the nebulizer unit 75 is similar to that heretoforedescribed including the nebulizer housing 39 .defining a nebulizerchamber 40 and opening into a bore 45 leading to the transducer (notillustrated). The lower end of the nebulizer chamber 40 is closed by thetransducer and by the cap 56. An electrical jack 66 provides theconnection to the oscillator power supply 100.

As in the embodiment of FIGS. 1 through 8, the nebulizer chamber 40 isfilled with a suitable liquid 43, such as distilled water, to the liquidlevel 44 to be driven by the transducer 15. Since the liquid 43 in thechamber 40 does not. escape therefrom, there is no need for a fail-safedevice, such as the photoelectric control unit 58 heretofore described,and accordingly the fluid conduit 62 extending from the lower end of thenebulizer chamber 40 may be closed by a plug 76.

To hold the medication, a somewhat conically shaped plastic bag isproportioned to'hang into the water so that medication 81 contained inthe bag 80 can be nebulized. The liquid 43 resting on the transducer isnot nebulized, but a focal point of the liquid is effectively definedwithin the body of medication in the plastic bag 80. The plastic bag 80,as best illustrated in FIGS. 12 and 13, includes a cylindrical capmember 82 through which extend a gas inlet and gas outlet nipple 83 and84, respectively. A bag member 85 of generally conical shape and formedof pliable material which will transmit the ultrasonic vibrations, suchas of plastic film, is hung into the nebulizer housing 39 so as toeffectively divide the housing 39 into an upper compartment 40a and alower compartment 40b. The upper edge of the bag member 58 contains amolded flange 86 having an inwardly facing groove 86a receiving theperipheral edge of the cap member 82.

Since the medication 81 is contained within the upper compartment 40a,it is necessary that the gas flow through the gas supply conduit 26passes through the upper compartment 400 to flush out the nebulizedmedication and entrain the same into the gas flow in the supply conduit26. To this end the conventional gas inlet and gas outlet conduits 70and 71 heretofore described are replaced by gas inlet and gas outlet conduits 90 and 91. The gas inlet conduit 90 includes an inlet tee 92having one end thereof conncctedto the outlet 70b extending into thenebulizer housing 39, and the gas outlet conduit includes an outlet tee93 also having one end connected to the inlet portion 71b extending intothe nebulizer housing 39. The outlet portion 70b and the inlet portion7112, however, are plugged by a suitable plug member 95 so that gasaccess into the lower compartment 40b is blocked and the lowercompartment 40b is essentially a closed or sealed compartment. The inlettee 92 has an inlet portion 92a facing upstream in the gas supplyconduit 26, and the other end 92b of the tee 92 is connected through asuitable elbow 96 and flexible conduit line 97 to the gas inlet nipple83 in the cap member 82. The outlet tee 93 has a discharge portion 930facing downstream, and another leg 93!] of the tee 93 is connectedthrough an elbow 98 and flexible conduit 99 to the gas outlet nipple 84extending through the cap member 82.

From the preceding brief description of the medication bag within thenebulizer unit 75, the operation thereof is believed clear. However,briefly, it will be understood that the liquid 43 resting on thetransducer is not nebulized, but a focal point or vortex of the liquidis effectively defined within the body of medication 81 in the bag 80.The medication 81 in turn is nebulized in the upper compartment 40a ofthe nebulizer housing 39. The dynamic or impact effect of gas flow inthe gas supply conduit 26 will be effective to circulate a portion ofthe gas stream through the upper compartment 40a to flush out thenebulized medication and to disperse the nebulized medication into thegas flow.

Advantageously, the disclosed modification, including the medicationbag, has the advantage of being disposable so that each patient may havehis own, and apparatus cleaning is substantially reduced. Moreover, itis a further advantage that when only small amounts of medication arerequired, such as 35 cc., that this is the total amount of medicationthat is used, rather than the greater amount, such as cc., which wouldbe required to operate without the medication bag. A bag proportioned tohold 35 cc. of medication will actually nebulize about 33 cc. thereof sothat the waste is negligible.

Moreover, it is understood that the normal gas inlet and outlet into thenebulizer housing may be closed since the gas inlet and outlet now openinto the bag.

Although the present invention has been described by reference to only asingle embodiment thereof, it will be apparent that numerous othermodifications and embodiments will be devised by those skilled in theart which will fall within the true spirit and scope ofthc presentinvention.

What we claim as new and desired to be secured by Letters Patent oftheUnited States is:

1. In an oxygen tent apparatus comprising a canopy, a temperature andflow control unit for regulating the flow of a gaseous medium to saidcanopy, and gas conduit means for connecting said unit and said canopyto provide a flow ofgaseous medium between said unit and said canopy,the improvement comprising:

an ultrasonic nebulizer for entraining minute particles of liquid into agaseous medium including a housing defining a vapor chamber positionedadjacent said gas conduit means and in close proximity to the junctionof said gas conduit means with said canopy,

a pair of conduits connecting said conduit means to the interior of saidnebulizer housing, a first of which conduits opens into said as conduitmeans facing u stream and a second of whic conduits opens into sai gasconduit means facing downstream, to direct a portion of the gaseous flowinto said canopy through said vapor chamber.

2. The combination set forth in claim 1 wherein the nebulizer includesmeans for maintaining a level of liquid in the vapor chamber, apiezoelectric transducer at the bottom of the vapor chamber, and highfrequency electrical power source means connected to said transducer forenergizing said transducer.

3. The combination set forth in claim 1 including a reservoir ofliquidconnected to supply liquid to said chamber.

1. In an oxygen tent apparatus comprising a canopy, a temperature andflow control unit for regulating the flow of a gaseous medium to saidcanopy, and gas conduit means for connecting said unit and said canopyto provide a flow of gaseous medium between said unit and said canopy,the improvement comprising: an ultrasonic nebulizer for entrainingminute particles of liquid into a gaseous medium including a housingdefining a vapor chamber positioned adjacent said gas conduit means andin close proximity to the junction of said gas conduit means with saidcanopy, a pair of conduits connecting said conduit means to the interiorof said nebulizer housing, a first of which conduits opens into said gasconduit means facing upstream and a second of which conduits opens intosaid gas conduit means facing downstream, to direct a portion of thegaseous flow into said canopy through said vapor chamber.
 2. Thecombination set forth in claim 1 wherein the nebulizer includes meansfor maintaining a level of liquid in the vapor chamber, a piezoelectrictransducer at the bottom of the vapor chamber, and high frequencyelectrical power source means connected to said transducer forenergizing said transducer.
 3. The combination set forth in claim 1including a reservoir of liquid connected to supply liquid to saidchamber.